WASHINGTON, Iowa -- The Washington County Attorney's Office on Friday announced that it is dismissing a drunken driving charge against Keokuk County Sheriff Jeffrey Earl Shipley, 46, on the condition he receive alcohol evaluation and treatment.

Although Shipley no longer is facing criminal charges, the Iowa Department of Transportation now lists his driver's license as invalid, a penalty under Iowa Code for refusing to consent to a blood alcohol content test.

It's unclear how Shipley's suspended license will affect his ability to do his job. Shipley on Friday declined to comment, and an official in his office also refused to answer questions.

Washington County Attorney Larry Brock said Friday that his office had sufficient evidence to prove Shipley guilty of OWI, but there were "additional factors" that led prosecutors to conclude they had a less than 50 percent chance of convincing a jury in Keokuk County to convict Shipley.

"The trial would take place in Keokuk County where Sheriff Shipley was elected in 2008 by receiving 49 percent of the vote in a four-person race," Brock said. "Sheriff Shipley received the most votes in 14 out of 17 precincts thereby indicating that Sheriff Shipley received strong and widespread support throughout Keokuk County."

Brock said his office also deferred prosecution because Shipley was "still coping with the tragic events" involving a fatal shooting of Keokuk County Deputy Eric Stein on April 4.

When asked if Shipley received special treatment, Brock said, Shipley did not.

"This case was a borderline case," he said.

Shipley was not falling-over drunk, did not have slurred speech and refused to take blood alcohol content tests, leaving them without hard evidence, according to Brock.

Still, he said, investigators felt Shipley was guilty of OWI.

"One of the stronger pieces of evidence was his refusal to take a test," Brock said, adding that if Shipley really had consumed only one beer, like he claimed, he would not have tested above the legal driving limit and should have been fine to take a test.

Among other evidence investigators had toward proving Shipley's guilt was the "very strong odor of alcohol" coming from him when an Iowa State Patrol trooper initially pulled him over about 8 p.m. July 27 near the intersection of Highway 92 and Stone Street in Sigourney.

Shipley's eyes were watery and bloodshot, and the trooper noticed Busch Light beer cans behind the passenger seat of his truck, which also smelled of alcohol, according to an investigation report released Friday.

Shipley, who had his 19-year-old daughter in the truck with him when he was pulled over, admitted to having one beer with his supper, according to the report. He had difficulty finding his registration papers when asked for them, the report states, and Shipley handed the trooper his concealed weapons permit when asked for his driver's license.

Investigators said Shipley also "engaged in behavior which can be used by persons suspected of OWI to mask the odor of alcohol and interfere with certain breath tests," according to the report. Brock wouldn't elaborate on those behaviors.

Shipley didn't cooperate with field sobriety tests, he refused to go to the booking room once taken to the law enforcement center, and he asked "why he was not being given any professional courtesy," the report states. Shipley told a sergeant that he "knew (Shipley) could not take the tests."

"Sheriff Shipley did not provide any details as to why he felt he could not take the tests," according to the report.

This summer's incident was not Shipley's first alcohol offense. Shipley pleaded guilty on Nov. 25, 2008, to operating a motorboat while intoxicated. He was sentenced to pay fines and spend two days in jail in that case, according to Iowa court records.

Brock stressed that members of the public shouldn't think they can get out of an OWI prosecution simply by refusing to take the tests. And, according to Iowa law, test refusal results in a one- to two-year license revocation.

Brock said Washington County has not deferred prosecutions in any other OWI cases. J. Dean Keegan, a criminal defense attorney in Iowa City who handles mostly OWI cases, said that although deferred prosecutions are not commonplace in drunken driving cases, they are not rare either.

"There might have been probable cause to arrest," he said, but proving it beyond a reasonable doubt is "a significantly higher standard."

Even though a person can lose their license for refusing to submit to chemical testing, Keegan said, the test results can be irrefutable.

"It's not a surprise to me whenever someone in law enforcement decides not to give a breath test," he said. "They understand how easy it is to convict once you meet that number."